The invention relates to printing apparatus and particularly to the aspect of such apparatus for applying ink to a surface on which an image is disposed which is to be applied to another surface. While the invention has particular application to flexotype apparatus and particularly to such apparatus utilized for marking lumber, it will be understood the invention also has application to other printing apparatus. In flexotype printing apparatus, ink disposed on a first roller is applied to a second roller on which an image is disposed. The image on the second roller is then passed over the lumber or other surface on which the image is to be printed. This is in contrast to offset printing in which print ink on a first roller is applied to a second roller which is then applied to a roller on which the image to be printed is disposed.
In the lumber and panel industry there is a requirement to identify individual pieces of lumber and panels with grade markings. Some prior art apparatus does use a roll which has a substantially solid circumferential face in which the ink is disposed. This arrangement is in contrast to liquid ink feeding apparatus. The ease with which the ink is transferred to the printing element or image before it is transferred from the image to a piece of lumber is of great importance. If proper inking occurs, the ink is tranferred and a complete image will be produced on the lumber. If too much or too little ink is transferred, the printing will be illegible on the lumber.
The prior art apparatus has used ink rolls of the same general type as that used in the present invention with external sources of heat to promote the proper flow of ink out of the roll and onto a printing element. Typical external sources include heaters such as electrical resistance heaters and infra-red lamps. The apparatus used in the prior art suffers from several disadvantages. An approach which heats the entire area of the roll inherently consumes a large quantity of energy while being relatively ineffective in placing the heat at the precise location of the ink roll where it is most needed. Still other problems with such heaters result from the location of the space heaters or infra-red lamps which may result in physical damage to the heaters or lamps. In still other cases the heaters or lamp may be inadvertently positioned so close to the ink roll that the ink roll will begin to smoke because the source of heat is too close.
Another problem encountered with the prior apparatus is that the use of such external heaters mandates the use of a relatively small diameter ink roll which results in a relatively sort service life and, thus, relatively high cost. It will be understood that in the existing apparatus the ink rolls must be replaced at intervals as short as one hour.
Still another problem with the prior art apparatus is that it is sensitive to the ambient temperature and, thus, typically will not work well in cold temperatures and, more specifically, will not work well in the cold temperatures which are commonly encountered in many logging areas.
It is an object of the present invention to minimize power consumption and eliminate heat lamps and space heaters and, thus, consequential breakage of such heating sources as well as to more effectively heat the interior of the ink roll.
It is another object of the invention to provide apparatus which will enable the use of relatively larger diameter ink rolls than was possible when utilizing the prior art structures, which will result in lower costs.
It is still another object of the invention to provide apparatus which will function well despite the ambient temperature.